The principal pollutants produced in the case of diesel internal combustion engines are oxides of nitrogen and soot particles. The production of the nitrogen oxides is promoted by a relatively high concentration of oxygen by comparison with the fuel mass in a combustion process of the internal combustion engine. A low oxygen concentration prior to the combustion process can lead to a low oxygen concentration after the combustion process in an exhaust gas of the diesel internal combustion engine. However, the low oxygen concentration in the exhaust gas of the diesel internal combustion engine leads to a high rate of production of soot particles.
In an internal combustion engine that is disposed for example in a motor vehicle, exhaust gas from a combustion process of the internal combustion engine can be supplied to a new combustion process in order to reduce the pollutant emissions, in particular the nitrogen oxide emissions. Recirculating the exhaust gas and mixing the exhaust gas with fresh air for the new combustion process results in a lower production of nitrogen oxides during the combustion process. If the internal combustion engine includes a lambda probe whose measurement signal is indicative of an air/fuel ratio of the exhaust gas, then it is possible to monitor as a function of the measurement signal of the lambda probe whether an exhaust gas recirculation rate is being implemented as desired. However, providing the internal combustion engine with the lambda probe is associated with additional costs compared with an internal combustion engine without lambda probe.